Notice Your Car Vibrating at Higher Speeds? It Could Be More Serious Than You Think Barry's Auto Body Car Vibrates When Idle: Major Causes and More dubizzle Why Does My Car Shake at Idle but Smooth Out While Driving? Vibrating while idling in drive If your car shakes at high speed the cause is often mechanical imbalance. Small issues become more noticeable as speed increases. Unbalanced tires are a common reason, creating vibration that grows